locking/lockdep: Fix bad recursion pattern

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There were two patterns for lockdep_recursion:

Pattern-A:
	if (current->lockdep_recursion)
		return

	current->lockdep_recursion = 1;
	/* do stuff */
	current->lockdep_recursion = 0;

Pattern-B:
	current->lockdep_recursion++;
	/* do stuff */
	current->lockdep_recursion--;

But a third pattern has emerged:

Pattern-C:
	current->lockdep_recursion = 1;
	/* do stuff */
	current->lockdep_recursion = 0;

And while this isn't broken per-se, it is highly dangerous because it
doesn't nest properly.

Get rid of all Pattern-C instances and shore up Pattern-A with a
warning.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200313093325.GW12561@hirez.programming.kicks-ass.net

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This commit is contained in:

Peter Zijlstra 2020-03-13 09:56:38 +01:00

parent 25016bd7f4

commit 10476e6304

1 changed files with 40 additions and 34 deletions

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74

kernel/locking/lockdep.c

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